Electrical Circuit Breakers – MHC Mohamed Harb Contracting

A circuit breaker is an automatically operated electrical switch designed to protect an electrical circuit from damage caused by:

• Overload (current exceeding normal levels for a prolonged period),

• Short circuit (direct connection between conductors causing a surge of current),

• Ground fault or leakage,

• Arc faults, which can cause electrical fires.

Unlike fuses, which must be replaced after a fault, circuit breakers can be reset and reused.
They combine mechanical and thermal-magnetic mechanisms to detect abnormal conditions and disconnect the electrical flow before serious damage occurs.

To ensure compatibility and safety, engineers must carefully review several specifications before selecting a circuit breaker.

4.1 Rated Current (In)

This defines the maximum continuous current the breaker can carry without tripping under normal conditions.

4.2 Breaking Capacity

The maximum current the breaker can safely interrupt during a short circuit, usually measured in kiloamperes (kA). Higher breaking capacity ensures safer operation.

4.3 Trip Curves (B, C, D)

Trip curves define the breaker’s response to overload:

• B-curve: Trips at 3–5× rated current (used in residential systems).

• C-curve: Trips at 5–10× rated current (used in general commercial applications).

• D-curve: Trips at 10–20× rated current (used for motors and high inrush currents).

4.4 Number of Poles

• Single-pole: One live wire (for 230V systems).

• Double-pole: For two live wires or live + neutral.

• Three-pole: For three-phase systems.

4.5 Rated Voltage

The maximum voltage the breaker can handle (e.g., 230V AC, 400V AC, or 690V for heavy-duty breakers).

4.6 Standards and Certifications

MHC follows international and Egyptian standards:

• IEC 60947 (Industrial)

• IEC 60898 (Residential/Commercial)

• Egyptian Standard ES 4819 for low-voltage switchgear.

➡️ Reference: Voltiat – Switchgear Types

Selecting a circuit breaker is not a random choice; it requires engineering analysis and field experience.

5.1 Load Analysis

• Identify total and individual loads (lighting, HVAC, elevators, motors, etc.).

• Calculate peak demand and diversity factor.

• Ensure cable capacity matches the breaker rating.

5.2 Electrical Distribution Coordination

• Proper layout of distribution boards.

• Balance load between phases.

• Provide easy access for maintenance and isolation.

5.3 Safety and Reliability

• Use RCCB or GFCI breakers in wet or human-accessible areas.

• Implement surge protection devices alongside breakers.

• Always verify the breaker’s conformity to standards before installation.

5.4 Cost and Quality Balance

• The cheapest breaker isn’t always the safest.

• Choose reputable brands with proven durability and certified testing.

• Consider after-sales support, warranties, and spare parts availability.

Since our establishment, MHC – Mohamed Harb Contracting has encountered various real-world challenges:

6.1 Global Economic Fluctuations

Price volatility in imported electrical materials and exchange rate instability affected project costs and supply timelines.

6.2 Material Shortages

During certain years, delays occurred in sourcing MCCBs, RCDs, and other electrical components due to global manufacturing disruptions.

6.3 Compliance with Government Quality Standards

Working with entities such as the Ministry of Electricity, the Egyptian Electricity Holding Company, and Canal Distribution Company requires strict adherence to specifications and test certificates.
Even minor deviations can delay approvals or lead to rejection of installed components.

Our company provides complete electrical contracting services, focusing on safety and precision.

7.1 Design and Selection

We perform full system design, load estimation, breaker sizing, and selection of brands that meet project requirements.

7.2 Government and Corporate Projects

MHC has executed installations for major entities — from the Arab Contractors to government ministries — ensuring strict compliance with quality control and documentation standards.

7.3 Maintenance and Upgrades

We provide periodic inspections, preventive maintenance, and system upgrades, including replacement of outdated breakers with smart or differential protection models.

• Regular Visual Inspection
  Check for discoloration, deformation, loose terminals, or signs of overheating.

• Electrical Testing

  • Perform insulation resistance and continuity tests.

  • Test trip mechanisms and differential function (for RCCB/GFCI).

• Replacement Policy
  Replace breakers that show frequent tripping or reduced performance.

• Documentation and Traceability
  Maintain records of testing, servicing, and breaker performance to ensure traceability and compliance.

At MHC – Mohamed Harb Contracting, our goal is to become a leading force in Egypt’s electrical contracting industry through innovation, quality, and safety.

Circuit breakers might seem small components, yet they are crucial to protecting entire systems and lives. As we continue to expand, we plan to:

• Invest in smart protection systems and IoT-enabled circuit breakers.

• Build partnerships with local suppliers to ensure cost-effective sourcing.

• Provide ongoing training for engineers and technicians to keep up with the latest standards and technologies.